The present invention provides a novel process for the extraction, purification and concentration of polyphenolics from whole grapes, grape pomace and grape seeds. The liquid and powdered products of the present processes are particularly rich in polyphenolics, including anthocyanins, catechin monomers and their oligomers. These oligomers are frequently referred to as procyanidins in the field of polyphenol chemistry.
Polyphenolic extracts from grape components have acquired special attention in the nutraceutical and food and beverage industries due to their widely publicized ability to function as antioxidants. The well known epidemiological studies conducted in France examined the protective effects of red wine consumption in reducing cardiovascular diseases. Such effects, described in the well-known xe2x80x9cFrench Paradoxxe2x80x9d study, are strongly correlated to the presence of polyphenols in wine. Other studies indicate that red grape juice has antioxidant and platelet control activity comparable to that of red wine.
It is known in polyphenol chemistry that polyphenol compounds from vegetable sources can be extracted with aqueous solvents such as aqueous acetone, aqueous ethanol and aqueous methanol. Aqueous ethanol containing 50-80% ethanol is commonly utilized for such extractions.
It is also known that acetone and alcohols can be utilized to efficiently extract gallic acids, catechin monomers (i.e. catechin, epicatechin, epicatechin gallates), and oligomeric procyanidins from grape seeds. Extraction with acetone and alcohols yields oligomeric procyanidins with a degree of polymerization (xe2x80x9cDPxe2x80x9d) of 2 to 7 and polymeric procyanidins with a DP of up to 16.
U.S. Pat. Nos. 3,435,407 and 4,698,360 disclose a method for the extraction of proanthocyanidins from pine bark, to the exclusion of the accompanying polymeric polyphenols (condensed tannins) comprising sodium chloride extraction and precipitation. These methods require repeated extraction with ethyl acetate. The ethyl acetate is then reduced by evaporation, and oligomeric procyanidins are precipitated by the addition of chloroform. The methods disclosed in these patents, however, are not commercially practicable or safe. These methods rely on solvent-solvent partition processes which require special handling, with explosion proof equipment and facilities. In addition, the resultant oligomeric bark extract commercial product may not be readily marketable as it may require label disclosure of the presence of solvent residues.
U.S. Pat. No. 5,484,594 is directed to a multistage process for preparing grape seed extract rich in procyanidolic oligomers. The ""594 patent discloses extraction of seeds with 80% aqueous acetone, evaporation of the solvent and concentration of polyphenols. These steps are followed by refrigerated storage for 24 hours to precipitate polymeric procyanidins, and filtration. The method of ""594 further includes ultrafiltration of the extract to remove high molecular weight substances and an additional ultrafiltration with tighter molecular cut off membranes to further minimize high molecular polymeric procyanidins. The ultrafiltration permeate is extracted repeatedly with ethyl acetate to remove catechin monomers. The extract is further extracted with ethyl acetate to exhaustion in order to extract all oligomeric procyanidins. The organic phase is concentrated under vacuum and the oligomers are precipitated by the addition of methylene chloride. The precipitate is centrifuged and dried at 50xc2x0 C. under vacuum for 24 hours to purified powdered extract.
The practical utility of the multi-step solvent dependent process of the ""594 patent is limited due to the acetone extraction required to remove unwanted polymeric procyanidins from the grape seed, removal of which then requires several additional steps, such as selective membranes and solvents. Also, solvent residues tend to remain in the dried extracts.
U.S. Pat. No. 5,912,363 relates to a method for extraction of proanthocyanidins from plant material. The ""363 patent discloses heating an aqueous solid plant material mixture at temperatures of up to 350xc2x0 F. under increased pressure and/or reduced oxygen, followed by membrane filtration, preferably ultrafiltration, to produce a permeate containing extracted proanthocyanidins. The extracted proanthocyanidins are then separated from the permeate by contacting the permeate with an adsorbent resin. All the examples are carried out at a temperature of 240xc2x0 F., over the boiling point of water at atmospheric pressure.
The process disclosed in the ""363 patent is characterized by both a limited practicality and a less than optimal purity of the proanthocyanidin extract. It is believed that the use of high temperature necessitates the use of membrane filtration, and limits the practical utility of this method.
The present invention provides a novel process that allows for extraction, purification and concentration of polyphenol substances from whole grapes, grape seeds and grape pomace without the need for membrane filtration. Aspects of several embodiments of the novel processes disclosed herein include hot water extraction; a dual pH treatment of the hot water extracts, and the uses of a copolymer of trimethylolpropane trimethacrylate (xe2x80x9cTMPTMAxe2x80x9d), commercially available as XAD-7HP(copyright), as an adsorbent resin to maximize the concentration and purification of beneficial polyphenolic substances.
The processes of the present invention produce a highly concentrated polyphenol product by maximizing extraction of monomeric and oligomeric procyanidins and minimizing extraction of polymeric procyanidins. The instant invention does not require solvent extraction of the source materials, membrane filtration, or solvent-solvent partitioning. As such, the processes of the present invention are safer, simpler and higher-yielding than those previously known. The present invention is thus better-suited for large scale commercial/industrial and winery production than previously known methods.
The products produced by the instantly claimed processes may be used in foods, beverages and nutraceuticals as an antioxidant and to help lower the incidence of cardiovascular diseases; and in cosmetic preparations as an antioxidant. Antioxidant properties are beneficial across a wide range of applications. Thus, foods, beverages, dietary supplements, nutraceutical products and cosmetics containing the polyphenolic products of the instantly claimed processes may be produced. The highly concentrated polyphenol product of the whole grape processes of the present invention is also rich in anthocyanins and oligomeric procyanidins. The whole grape extract, in liquid or powder form, may be used as a colorant in food products, beverages, cosmetics and dietary supplements.